1. Field of the Invention
This invention relates to a brake device for bicycle, more particularly to a brake shoe for braking bicycle.
2. Description of the Related Art
FIGS. 1 and 2 illustrate a conventional brake device 10 which includes an elongated rubber brake shoe 11, and a metal connecting rod 12 fixed perpendicularly at the middle of one side of the rubber brake shoe 11. The rubber brake shoe 11 has a plurality of grooves 111 at intervals, each of which is defined by a pair of opposing groove walls 115, and a plurality of contact faces 112 spaced apart by the grooves 111. Each contact face 112 has a planar surface. The planar surface of each contact face 112 abuts completely against a wheel rim 13 when the rubber brake shoe 11 is operated to press against the wheel rim 13. Thus, a braking effect can be easily obtained from the brake device 10. However, because the planar surface completely contacts the wheel rim 13 upon braking, the wheel may immediately reach dead-lock, causing the bicycle to overturn. Furthermore, as the contact faces 112 are elastic, upon braking, they will deform and vibrate between their original position and a position shown by phantom lines in FIG. 3.
FIGS. 4 and 5 illustrate another conventional brake device 20 for overcoming the above-mentioned problem of immediate dead-lock action. The brake device 20 includes an elongated rubber brake shoe 23 having one side inserted into a shoe holder 21 and fixed thereon by screw means 211. A connecting rod 22 is secured on the shoe holder 21 and is perpendicular to the rubber brake shoe 23. The rubber brake shoe 23 has a plurality of grooves 231 disposed at intervals on the other side of the rubber brake shoe 23, and a plurality of inclined contact faces 232 spaced apart by the grooves 231. Each of the inclined contact faces 232 has a tip portion 233 at one end of the contact face 232. The tip portion 233 of the inclined contact face 232 first contacts the wheel rim 24 upon braking, and afterwards, the following portion of each inclined contact face 232 gradually contacts the wheel rim 24 by the continued braking action. The brake device 20 can gradually brake the wheel without causing the bicycle suddenly moving into a dead-lock position and overturn. However, like the upper edges 113 of the brake shoe 11 shown in FIGS. 1 and 2, the tip portions 233 can be trailed and vibrated by the forwardly moving wheel rim 24 shown in FIGS. 6 and 7, thereby generating uncomfortable noise.